Category: Admin’s blog

The need of an universal PC/radio interface had triggered me to develop this board. Even at the first version I’ve already sold out all the available units so, actually I’m very happy about how it was wellcomed by Ham Radio operators. What differentiate this board from any other commercia board?

• Fully opto-insulated CI-V / CAT interface for Yaesu and ICOM radios 3kV ESD rated
• Fully opto-insulated PTT/Key output 3kV ESD rated
• State-of-the-art Bourns audio coupling transformer with -0.3dB flatness between 200-3000kHz band 3kV ESD rated
• Fully separate PC/radio masses
• Universal radio connector on DB9 female socket. Just wire the cable according to your radio pinout!
• Two separate USB ports one for radio control and PTT/key and one for Audio stream
• Integrated USB audio codec: it acts as an USB audio card leaving in peace yours computer one!

FTDI is the manufacturer of the USB UART chip that this board uses for the CAT/CI-V and PTT. It’s not a fake chinese copy. You can use MProg 3.5 software from FTDI to modify lines polarities if needed like in case of CI-V reverse polarity signals. You can download MProg >>HERE<<

This first version have no enclosure available, neverthless it works without RFI issues. I’m planning to make a 3D printable model for my second revision.

Here you can download it’s manual as pdf >>HERE<<

It’s drivers for audio and FTDI chip are >>HERE<<

This is the procedure of how to use it on Windows 7 & 10 with Ham Radio Deluxe

From “System device manager” you have to identify the “USB Serial Port” and put it’s identification number “COM22 as example” into HRD startup config dialog. Select also your radio manufacturer, model and baud rate.

Once the HRD to radio connection successed you can configure the “PTT” line as active on “RTS” line asserted. Sometimes thisis not needed because HRD can assert software PTT triggering.

In DM780 open the settings and use PTT by HRD option that you’ve already configured.

The USB audio card is avaiable as audio in/out. Please deactivate mike AGC otherwise your signal will be degraded.

Recently I’ve tested this super simple circuit capable to collect pulses from a SiPM and amplify and pulse-shape them. The pulse shaper Tau constant is 250uSec, this way the resulting shaped pulse could be directly sampled by a PC audio card via Mike input line.

The resulting prototype was made by etching it over a single side bakelite PCB board.

There is no 32-45V power supply for the SiPM polarization. I’ve obtained it by a series of 4x 12V alcaline batteries followed by a linear regulator. SiPM diodes are very sensible to supply noise… batteries in their simplicity provide excellent noise performance.

The shaped pulse looks good and performs well. Tested with my PC soundcard and an 8x8x50mm CsI(Tl) crystal.

FWHM is acceptable. The opamp used must be swapped with something with better bandwidth gain.

This is an ultra short user guide for cold war CCCP made DP-5B geiger counter.

The battery elements are located into a bottom compartment. You can get them by opening and splicing the 3x 1.5V elements of a 4.5V flat battery pack. I’ve then wrapped with heathshrink pipe to be insulated against each other.

The first thing to do after switching on is setting the voltage converter. Actually that’s the first position after had clockwise rotated the main selector. The needle must be into the black mark zone of the scale. Use the voltage regulation knob carefully… the “peak'” of the correct position is very sensible.

The second thing is rotate main selector to the first position of the lowest scale. You must do that to zero the instrument. Now you can measure gamma or beta sources and change the various scales.

This is with gamma filter off.

Gamma filter on and 0 because of background.

This is a radium tube with strong gamma emission. I’ve shut down my lab’s light to show the phosphorescent dials.

This is with backlight ON.

The device have it’s own check source. 100kBq Sr90 under a protective cover that can be rotated to put the probe into a precise position.

Inspired by the work made by Lukas and published by him into this post LINK, I’ve tried to replicate his experiment. I’ve choosed to change some ingredients like epoxy and wavelength shifter. He uses E45 epoxy but I’ve preferred E30 because is more clear with better optical properties. He also uses cumarine-102 but cumarine-1 matches better the PPO 2,5-Diphenyloxazole emission spectra.

“Standard mixture” to make a 32gr plastic scintillator sample I use:

• Epoxy E30 part A (base) 20gr
• Epoxy E30 part B (hardener) 12gr
• PPO scintillator 0.32gr
• Cumarin-1 0.032gr

The procedure:

• Heat part A at 80⁰
• Dissolve PPO + cumarin-1 into part A
• Re-heat again solution to 80⁰
• Add part B heating when stirring for 5 minutes
• Pour into a suitable mould like HDPE plastic or silicon
• Put the mould with epoxy over a 3D printed heath bed setted at 80⁰C and let it stay for 2h aprox. This way the 3D printed heath bed acts as an heather helping the epoxy catalisys.
• I use hot air gun for soldering SMD to heath part A at the start of the procedure simply carefully blowing hot air over the epoxy and stirring to dissolve PPO + cumarin-1

Results show that this kind of epoxy-based scintillator is sensible with alpha beta and gamma rays but especially sensible to beta radiation.

I’ve also made a test to demostrate the effectiveness of cumarin-1 as wavelenght shifter. I’ve made a scintillator without it and… it doesn’t scintillate. Actually it scintillate into UV so I cannot se it!

On the left a standard mixture on the right without cumarin-1.

Standard mixture glows bright even in daylight if excited with enought UV from an UV lamp.

The effect is even more drammatic at night.

Neutrons are cool. Them are the key ingredient of any nuclear chain reaction, the trigger wich split the atom, the “biliard ball” that striking other atoms turns them in radioactive isotopes. Bothe and Becker in 1930 made them for first by “bombing” Beryllium with alpha rays emitted from Polonium 210. Why not try to replicate?

Po210 is not simple to be aquired in Italy expecially into high quantity needed to make a measurable ammount of neutrons. Actually the ony way that I’ve find  to get some was to buy a Staticmaster brush cartridge from Adorama – USA – and pay it twice it’s price because of customs and shipping fees. The cartrige contains 2x 250uCi of Po210 enclosed into a safe metallo/ceramic alloy golden covered ribbon. Such quantity in Italy is completly illegal and Po210 is 20000 times more poisonous than cyanide. This product it’s otherwise completly safe if you don’t dismantle the source frm it’s location and respects only the USA regulations in matter of exempt quantity of radioactive isotopes. Beware!

Po210 half life is 138 days. Mine was made in Juy 2020 and I’m writing this post in March 2021. In total 243 days. My sample in a month will be 125uCi.

An interesting thing to do with it is also see how alpha’s can trigger luminescenze into a  ZnS(Ag) scintillation screen. To do that I’ve very carefully removed the sources from the staticmaster brush and glued over an alluminium sheet for handling.

It’s quiet impressive! It glows strongly than appares on picture. I’ve noticed by moving the scintillation screen that departing it from the source of just 3-5mm is enought to stop the effect. This means probably that just 3-5mm oof air are enought to stp the apha emitted by the Po210 source. Interesting.

Now let’s go back to the main topic. I’ve the Po210 now I need a beryllium target. This is quiet easy and legal to source. Just buy a smal sheet of pure beryllium from eBay. It’s commonly sold there in rods and sheets.

Now that I’ve the Po210 and the Be target how to measure the effective generation of neutrons? Luckly I’ve bought some time ago a Stilbene crystal scintillator. Stilbene is an organic solid scintillator material used for fast neutron detection. It’s quiet efficent indeed!

This crystal coupled with a photomultplier tube was my neutron detection scintillation probe. I’ve used it with an Eberline ESP1 scaler/rate meter.

I’ve take a series of 3 measures:

1. Background without source
2. Po210 no Be target
3. Po210+Be

The experiment was repeated 10 times. The difference between readings will show us what Stilbene is detecting. As example take a look at following pictures

As you can see I’ve got:

1. 4740 pulses background
2. 6340 pulses background + xray generated by alpha hitting the aluminium of the detector
3. 7300 pulses background + xray + something else… NEUTRONS!!! I’ve got it!

Considering uniform the background I can assume that I’ve generated 7300 – 6340 = 960 neutrons in 8 minutes that’s the time setted into ESP1 for counting. 2N/sec. My Po210 +Be source generated 2N/sec when it was at almost full strenght. My Stilbene crystal is small and probably many neutrons escaped counting but… yes I confirm, it works.

Sadly to try neutron activation of materials I need a stronger source of neutrons.

Recently I’ve designed and built a simple yet very nice playing guitar amplifier.

I’ve designed it keeping in mind that I don’t wanna distortion: it’s a specialized amplifier for playing contry music, blues and clean.

To reach this goal I have to minimize the overloading of the first input stage and keep low the overall gain.

I’ve choosed for this role an high-current low noise single triode tube tought by constructor to be used as preamplifier in audio stages with resistor-capacitor coupling.

The second stage it’s based uppon a dual triode – medium gain tube for UHF radio band receiver use with internal shield. It’s second triode is used as phase splitter that drives a couple of EL84 power tubes in class B.

Here the details, schematic and notes as PDF file. Click here for PDF >>> Building NOTES

I’ve used the following russian tubes:

• 6C3П-ЕВ (6S3P-EV) equivalent of EC86 as first input stage
• 6Н3П-ЕВ (6N3P-EV) equivaent of 2C51 as voltage gain stage and phase splitter
• 2x 6П14П (6P14P) equivalent of EL84 as push pull output stage

The transformers are home made, home caculated, self winded. I’ve used oriented grain EI core to limit power loss. The low range cutoff frequency of output transformer is calculated for 100Hz. Primary fractioning it’s a secret.

For the ultimate schematic please click to download the PDF file >>> Building NOTES

This is the original schematic. I’ve modifiedit during assembly because of some small errors. The phase splitter built around V2/2 was not working properly. I’ve solved by putting the 1M resy from grid to ground not between the 1.5k / 56k series at the chatode bias. I’ve let the 56k+1.5k still there for bias.

It have some little instability at full input gain… it needs to be further modified and inproved.

Here the calculations for the two transformers.

Output transformer:

• Column 29x36mm EI oriented grain
• 1429 + 1429 turns dia. 0.14mm CuEnameled 4k+4k primary push pull
• 44 + 44 turns dia. 0.8mm CuEnameled 4R+4R speaker output to get 0-4R-8R inpedance selection.

Power supply transformer:

• Column 29x36mm EI oriented grain
• 1123 turns dia. 0.25mm CuEnameled 220-230V mains input
• 1116 turns dia. 0.18mm CuEnameled 200V for amplifier main power
• 35 turns dia. 0.8mm CuEnameled 6.3V for filaments

I’ve made this cute 3D printed holder for EL84 tubes. It’s compatible only with western made tubes not Russians/Eastern block because holes  are 22mm diameter.

Here you can download Rinocheros 3D model, STL and GX files >>> EL84 holder

Some time ago I’ve won a 63×63 NaI(Tl) crystal for around 80€ at eBay. It is an SDN52 a special crystal designed to be heat and vibration resistant. Let’s build a probe with it and a 76mm photokatode XP2421/SQ PMT

First problem to solve was how to tightly couple this heavy crystal with this PMT? I’ve solved it with the help of my 3D printer: I’ve designed and printed a fitting with TPU that’s a kind of rubber filament material. STL zip file: gasket  password: madexp

And now let’s put all togheter.

Finally I’ve soldered in place the dynode chain voltage divider PCB.

After covering the tube with black tape I am ready to test it.

The result is a nice 7.5%-8% FWHM @ Cs137 peak

How to make a scintillation probe with aluminium enclosure? Is not that hard if you have a lathe, a mill and a drill. I start assembling the scintillation crystal with the photomultiplier and measuring them. From standard aluminium pipe size, I choose one for the body and one, as reducer, to fit the scintillator inside the body pipe. From an alluminium round bar I made the ened cap.

The crystal adapter is a piece of pipe shaped to fit inside the body pipe and have an inner hole where I put the crystal and photomultiplier. I use silicon black glue to gle everything together. It is strong but can be removed easily if I need to re-open the assembly.

To assemble the PMT+crystal I’m using an optical coupling grease.

After silicon glue hardened I assemble the voltage divider board to the photomultiplier wires. The divider board is home made etching it’s circuit on a piece of FR4 or bakelite copper clad board.

Now that everything is ready, I close the probe adding the end-cap and soldering the voltage divider + and – at the BNC female connector on the ending cap.

Usually I anodize my alluminium parts. Using different kind of alluminium alloys for different probe parts results in different color of the anodized surface.

And this is the final result